Steel and steel alloys have previously been used extensively in tubular structural elements, gun barrels, and the like, where continuous or transient internal pressures of high magnitude are encountered. In particular, machined or forged high-strength steel alloy tubes are used in forming gun barrels. Considerable precision and skill are required to manufacture a gun barrel by conventional processes leading to a fairly costly component. Some improvements have been suggested, particularly in attempts to reduce component weight and/or costs. The use of gun barrels fabricated wholly or partially by filament-winding a glass-fibre/epoxy composite, followed by curing, has been described previously, e.g., Canadian Pat. No. 582,160 of Aug. 25, 1959; U.S. Pat. No. 3,298,279 of Jan. 17, 1967; U.S. Pat. No. 2,847,786 of Aug. 19, 1958; and U.S. Pat. No. 3,517,585 of Jan. 30, 1970.
It is emphatically stated here, however, that all of these patents remain silent on the use of carbon-fibre/epoxy composite or describe a fully composite barrel which can fire no more than a few rounds. Indeed, U.S. Pat. No. 3,298,279 clearly states that a glass fibre/epoxy rifled barrel can fire only one round. Also, all previous patents remain silent on means for providing adequate stiffness to a fibre composite gun barrel or on the problems resulting from inadequate stiffness.
Notwithstanding the express teachings of the above patents, the present invention provides a number of advantages and features not previously known. The novel barrel sections described herein and the method of making the same are relatively inexpensive, light and provide good reliability. A gun barrel made entirely of the material described herein is useful and operative in certain applications where the prior art taught only the use of barrels that were wholly or at least partly metallic. The barrel sections described herein are light in weight, yet strong enough to withstand the transient high pressures generated in a gun system.
In particular, the barrel sections of this invention are very useful in a recoilless gun application. Typical recoilless guns in service, such as the U.S. 90 mm and 106 mm recoilless rifles, and the Swedish 84 mm Carl Gustaf recoilless rifle use costly, heavy, precision machined steel components. Other recoilless guns use glass-fibre/epoxy filament-wound material and are one-round, `throw-away`, weapons. An example of the latter type is the Swedish 84 mm AT-4. In contradistinction the present invention allows for the firing of 30 or more rounds before erosion of the inner surfaces of the barrel sections causes excessive degradation of weapon performance. Also, the gun barrel described herein may be used in other weapon systems such as field artillery pieces, rocket launchers, mortars, and other projectile launchers.
The advantages of the present invention may be best seen by comparing the performance of barrel sections fabricated as in the present invention and conventional sections. For example, the gun barrel of an 84 mm recoilless gun weighs 8.5 kg when fabricated from high-strength steel alloy and 2.8 kg when fabricated as per the teachings of the present invention. Operating pressures are about 9000 psi in both cases with the propellant gas temperature being about 3500.degree. K. The muzzle velocity in both cases is about 305 m/sec with all aspects of weapon operation being identical. It should be noted that the barrel of the present invention was fabricated automatically using a microprocessor-controlled filament-winding machine without the need for extensive machinist intervention. The weight and fabrication cost reduction is most important as it allows for greater issue to soldiers who will be able to give it more extensive use than is possible with either a heavy steel gun or a glass-fibre/epoxy gun.
The present invention represents an improvement over the concepts enumerated in copending, commonly assigned U.S. Pat. No. 4,485,721, issued Dec. 4, 1984. That application introduced the concept of a gun barrel produced entirely from a filament-wound fibre reinforced composite material. The gun barrel was produced so as to have inwardly directed projections formed from lengths of the composite material, the projections defining rifling lands within the barrel. In contrast to the teachings of the prior application wherein the composite fibre material was helically wound on a mandrel so that the fibres were oriented in mutually stress transmitting relation to each other, the present invention recognizes that the manner in which the fibre material is wound or placed on the mandrel can greatly affect the effectiveness of the resulting weapon, as can other factors such as the type of fibre and resin, the tension placed on the fibre tow during winding, and the cure cycle. In addition, by appropriately configuring the windings it is possible to produce a gun barrel per se, with or without rifling lands, or any other tubular weapon system component subjected to very high transient gas pressures and hot propellant gas erosion of its inner surfaces.